Polymerization of α-Methylstyrene with Potassium as Initiator. VIII. Glass Transition Temperature Study of Reaction Products

Abstract

A glass transition temperature (T) study on poly-α-methyl-styrene samples having bimodal molecular weight distributions composed of components D + A and B + C, was carried out with a DSC-2 differential scanning calorimeter. T data were also collected on binary blends of poly-α-methylstyrene samples prepared from narrowly dispersed low and high molecular weight polymers. Extrapolated T_ge (at q = 1°K/min) data of the bimodal polymers showed that the percent proportion, the molecular weight [Mbar]_n, and the steric configuration of component D + A play an important role in determining their overall glass transition temperatures, these being lower than those recorded for a unimodal polymer of the same [Mbar]_n. In binary blends of poly-α-methylstyrene, the overall glass transition is not affected by the presence of the low molecular weight component either because its steric structure differs with that of D + A or because of the fact that in binary blends the chain-end segments of the two components are not well packed.